Cell pack and method for producing and method for disassembling the same

ABSTRACT

A cell pack includes a plurality of unit cells arranged in an arrangement direction and a restraint mechanism for restraining these unit cells. The restraint mechanism includes: a first end plate portion disposed at an end portion in a first direction of the arrangement direction of the plurality of unit cells; a second end plate portion disposed at an end portion in a second direction of the arrangement direction of the plurality of unit cells; and a ring-shaped restraining hoop portion. A dimension in the arrangement direction between the first end plate portion and the second end plate portion of the restraining hoop portion is set such that a predetermined restraining pressure is applied in a direction of compressing the plurality of unit cells along the arrangement direction. A method for disassembling the cell pack is also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.16/220,286, filed Dec. 14, 2018, which claims priority based on JapanesePatent Application No. 2018-003872 filed on Jan. 12, 2018, the entirecontents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to a cell pack in which a plurality ofsecondary cells is arranged and bundled, and a method for producing anda method for disassembling the same.

In recent years, secondary cells such as lithium ion cells have becomeindispensable as portable power sources for personal computers, portableterminals and the like and also power sources for driving vehicles suchas electric vehicles (EV), hybrid vehicles (HV), and plug-in hybridvehicles (PHV) and power sources for power storage and the like.Further, for example, as disclosed in Japanese Patent ApplicationPublication No. H09-120808, Japanese Patent Application Publication No.2013-020740, Japanese Patent Application Publication No. 2015-187913,and Japanese Patent Application Publication No. 2002-343324, cells forapplications requiring a large capacity or high output are generallyconfigured in the form of cell packs in which a plurality of unit cells(battery cells) is stacked in a predetermined arrangement direction andbundled in order to connect the plurality of unit cells efficiently inparallel or in series. Japanese Patent Application Publication No.H09-120808 discloses a cell pack in which both ends of a cell stack aresandwiched between a pair of end plates, a restraining band is passedover the end plates, and the restraining band is fixed to the end plateswith a fastener.

In the cell pack, in order to prevent displacement of the unit cells dueto vibration, shock, or the like during use of the cells and to ensurecell characteristics, cell life and the like, restraining is sometimesperformed by applying a load in a direction of compressing which isperpendicular to the electrode surface of the unit cells. It is alsoknown that secondary cells repeatedly undergo volumetric expansion andcontraction in the course of charging and discharging. For this reason,a stress may be generated in the tensile direction from the cell stackto the end plates. In a configuration in which the end plates and therestraining band are restrained by a fastener, such a load easilyconcentrates on the fastener or the like, and the fastening member maybe plastically deformed or broken. When the fastening member isplastically deformed or broken, the restraint of the single cells isloosened, and it becomes impossible to maintain the restraining pressurenecessary for the unit cells.

SUMMARY

The present disclosure has been made in view of the above circumstances,and it is an object of the present disclosure to provide a cell packhaving a restraint mechanism which is unlikely to be loosened or brokeneven when a restraining pressure is applied which is higher than, forexample, in the related art, and also to provide a method for producingand a method for disassembling the cell pack.

The cell pack disclosed herein includes a plurality of unit cells(hereinafter may be referred to as “cell stack”) arranged in anarrangement direction and a restraint mechanism for restraining theplurality of unit cells. The restraint mechanism includes a first endplate portion disposed at an end portion in a first direction of thearrangement direction of the plurality of unit cells, a second end plateportion disposed at an end portion in a second direction of thearrangement direction of the plurality of unit cells, and a ring-shapedrestraining hoop portion including a first support portion disposed on asurface of the first end plate portion in the first direction, a secondsupport portion disposed on a surface of the second end plate portion inthe second direction, and a pair of side wall portions continuouslyconnecting the first support portion and the second support portionalong the arrangement direction. A dimension in the arrangementdirection between the first end plate portion and the second end plateportion of the restraining hoop portion is set such that a predeterminedrestraining pressure is applied in a direction of compressing theplurality of unit cells along the arrangement direction.

According to the above configuration, the restraint mechanism restrainsthe cell stack in the arrangement direction by the ring-shapedrestraining hoop portion. The restraining hoop portion has a ring shapeclosed in the longitudinal direction. Further, the pair of end plateportions is arranged inside the ring of the restraining hoop portion.Therefore, the reaction force of the cell stack against the restrainingpressure does not cause the end plate portion to be disengaged from therestraining hoop portion. As a result, it is unnecessary to fix therestraining hoop portion and the pair of end plate portions locally by afastener as in the related art. Further, for example, since there is noneed to hang the restraining hoop portion on the end plate portions, thecorners of the end portions in the end plate portions that are incontact with the restraining hoop portion can be curved. Thus, it ispossible to eliminate the locations where the stress concentrates in therestraint mechanism, and the loosening and breakage of the restraintmechanism are suppressed. For example, even when the cell pack is usedin an environment where vibrations occur, or when the cell pack isrestrained with a restraining pressure higher than that in the relatedart, it is possible to stably maintain a high restraining pressure for along time. In addition, highly stable cell performance in the cell stackcan be maintained over a long period of time.

In a preferred embodiment of the cell pack disclosed herein, therestraint mechanism includes two or more restraining hoops. In anotherpreferred embodiment, the unit cell includes a power generating elementincluding a positive electrode and a negative electrode, the restraintmechanism includes only one restraining hoop portion, and a dimension ofthe restraining hoop portion in a hoop width direction perpendicular toa surface forming the ring is equal to or greater than ½ of a dimensionof the power generating element in the hoop width direction. With such aconfiguration, the tensile strength of the restraining hoop portion inthe entire arrangement direction can be increased. As a result, it ispossible to stably restrain the cell stack with a higher restrainingpressure.

In a preferred embodiment of the cell pack disclosed herein, therestraining hoop portion is a seamless ring. Where the restraining hoopportion is formed in a ring shape including a seam, tensile stresssometimes tends to concentrate in the seam. Also, the seam tends to havelower strength against tensile stress than other parts. Therefore, byusing such a configuration, it is possible to increase the tensilestrength of the restraining hoop portions in the arrangement direction.Further, with such a configuration, it is possible to stably restrainthe cell stack with a higher restraining pressure.

In a preferred embodiment of the cell pack disclosed herein, therestraint mechanism is formed by integrally molding the first end plateportion, the second end plate portion, and the restraining hoop portionwith a single material. By integrally molding the restraint mechanism,it is possible to reduce the number of parts and realize a restraintmechanism with good handleability. Further, for example, by increasingthe width of the restraining hoop portion to match the dimension of theend plate portion, the restraining load can be dispersed and held in awider area, and a higher restraining pressure can be applied to the cellstack.

In a preferred embodiment of the cell pack disclosed herein, a slidingplate is interposed between the first end plate portion and theplurality of unit cells and between the second end plate portion and theplurality of unit cells, the sliding plate including a sliding surfacehaving a coefficient of friction of 0.5 or less on a surface in contactwith the first end plate portion or the second end plate portion. Withsuch a configuration, it is possible to easily arrange the cell stackbetween the pair of end plate portions. The advantageous result is thatit is possible to reduce the load applied to the cell stack at the timeof production.

In a preferred embodiment of the cell pack disclosed herein, the unitcell includes a power generating element including a positive electrodeand a negative electrode, and the negative electrode includes a metalmaterial that forms an alloy with lithium as a negative electrode activematerial. As described above, the restraint mechanism disclosed hereincan restrain the cell stack with a higher restraining pressure than inthe related art. Therefore, it is particularly preferable to use such aconfiguration, for example, for a cell pack including, as a unit cell, acell using a negative electrode active material of a metal material typewhich repeatedly undergoes large volumetric expansion and shrinkageduring charging and discharging.

In a preferred embodiment of the cell pack disclosed herein, the unitcell is an all-solid state cell including a positive electrode, anegative electrode, and a solid electrolyte. As indicated hereinabove,the restraint mechanism disclosed herein can restrain the cell stackwith a higher restraining pressure than in the related art. For thisreason, it is particularly preferable to use such a configuration, forexample, for a cell pack including, as a unit cell, an all-solid statecell that does not contain an electrolytic solution and has an increasedinternal resistance due to the interface resistance of the constituentmaterials of the power generating element.

In another aspect, the technique disclosed herein provides a method forproducing a cell pack. The production method includes arranging aplurality of unit cells in an arrangement direction to prepare a firstcell stack; arranging a first end plate portion and a second end plateportion so that the end plate portions are separated along thearrangement direction, and disposing a ring-shaped restraining hoopportion so as to surround the first end plate portion and the second endplate portion on planes parallel to the arrangement direction;displacing the first end plate portion in a third direction on a sideopposite to the second end plate portion in the arrangement direction sothat a separation distance between the first end plate portion and thesecond end plate portion is equal to or larger than a dimension of thefirst cell stack in the arrangement direction, and stretching therestraining hoop portion; inserting the first cell stack, such that thearrangement direction is the third direction, between the displacedfirst end plate portion and the second end plate portion; and releasingthe displacement of the first end plate portion and restraining theplurality of unit cells while applying a load in a direction ofcompressing along the arrangement direction to the plurality of unitcells by the first end plate portion, the second end plate portion andthe restraining hoop portion. With such a method, the restraintmechanism including the ring-shaped restraining hoop portion can beeasily installed at the cell stack.

In yet another aspect, the technique disclosed herein provides a methodfor producing a cell pack. The production method includes arranging aplurality of unit cells in an arrangement direction, disposing a firstsliding plate at an end portion of the plurality of unit cells in afirst direction of the arrangement direction, and disposing a secondsliding portion at an end portion of the plurality of unit cells in asecond direction of the arrangement direction to prepare a second cellstack; compressing the second cell stack in the arrangement direction sothat a dimension thereof in the arrangement direction becomes a firstdimension; preparing a restraint mechanism which includes a first endplate portion, a second end plate portion, and a ring-shaped restraininghoop portion and in which the first end plate portion and the second endplate portion are disposed opposite each other and spaced apart by afirst dimension along the arrangement direction and, in a plane parallelto the arrangement direction, the restraining hoop portion is disposedso as to surround the first end plate portion and the second end plateportion along the outer periphery thereof; installing an expansionsuppressing jig that prevents a separation distance between the firstend plate portion and the second end plate portion from spreading beyondthe first dimension; inserting the compressed second cell stack betweenthe first end plate portion and the second end plate portion; andrestraining the plurality of unit cells while displacing the expansionsuppressing jig in a direction in which the separation distance in thearrangement direction is increased and applying a load with therestraining mechanism to the plurality of unit cells in a direction ofcompressing along the arrangement direction. With such a configuration,the restraint mechanism including the ring-shaped restraining hoopportion can be easily installed at the cell stack.

The technique disclosed herein provides a method for disassembling acell pack including a first cell stack in which a plurality of unitcells is arranged in an arrangement direction and a restraint mechanismfor restraining the plurality of unit cells. The restraint mechanismincludes a first end plate portion disposed at an end portion in a firstdirection of the arrangement direction of the first cell stack; a secondend plate portion disposed at an end portion in a second direction ofthe arrangement direction of the first cell stack; and a ring-shapedrestraining hoop portion including a first support portion disposed on asurface of the first end plate portion in the first direction, a secondsupport portion disposed on a surface of the second end plate portion inthe second direction, and a pair of side wall portions continuouslyconnecting the first support portion and the second support portionalong the arrangement direction. The method for disassembling includes:displacing the first end plate portion relative to the second end plateportion in the first direction so as to extend the restraining hoopportion along the arrangement direction; taking out the first cell stackfrom between the first end plate portion and the second end plateportion; and displacing the displaced first end plate portion relativeto the second end plate portion in the second direction to release theextension of the restraining hoop portion. With such a method, it ispossible to disassemble the cell pack having the ring-shaped restraininghoop portion safely and easily.

In yet another aspect, the technique disclosed herein provides a methodfor disassembling a cell pack including a second cell stack in which aplurality of unit cells is arranged in an arrangement direction, a firstsliding plate is disposed at an end portion in a first direction of thearrangement direction of the plurality of unit cells, and a secondsliding plate is disposed at an end portion in a second direction of thearrangement direction of the plurality of unit cells; and a restraintmechanism for restraining the second cell stack. The restraint mechanismincludes: a first end plate portion disposed at the end portion in thefirst direction of the arrangement direction of the second cell stack; asecond end plate portion disposed at the end portion in the seconddirection of the arrangement direction of the second cell stack; and aring-shaped restraining hoop portion including a first support portiondisposed on a surface of the first end plate portion in the firstdirection, a second support portion disposed on a surface of the secondend plate portion in the second direction, and a pair of side wallportions continuously connecting the first support portion and thesecond support portion along the arrangement direction. The method fordisassembling includes: compressing the cell pack in the arrangementdirection so that the dimension of the second cell stack in thearrangement direction becomes a second dimension; preparing a pressurerelease area with a dimension in the arrangement direction equal to thesecond dimension at a position adjacent to the compressed second cellstack in a direction perpendicular to the arrangement direction of thecompressed cell pack; pressing the first sliding plate and the secondsliding plate of the compressed second cell stack in a directionperpendicular to the arrangement direction toward the pressure releasearea, and moving the second cell stack from a space between the firstend plate portion and the second end plate portion to the pressurerelease area; and releasing the compression of the compressed secondcell stack by enlarging the dimension of the pressure release area inthe arrangement direction with respect to the second dimension. Withsuch a configuration, it is possible to disassemble the cell pack havingthe ring-shaped restraining hoop portion safely and easily withoutextending the restraining hoop portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view schematically illustrating a cell pack accordingto one embodiment;

FIG. 2 is a side view schematically illustrating the cell pack of FIG.1;

FIG. 3 is a three-view diagram consisting of a plan view (a), a frontview (b), and a side view (c) schematically illustrating a unit cellaccording to one embodiment;

FIGS. 4A to 4D are side and front views schematically illustrating theconfiguration of the restraining hoop portion, and FIG. 4E is aperspective view schematically illustrating the configuration of an endplate portion;

FIG. 5 is a process diagram illustrating a method for producing a cellpack according to one embodiment;

FIGS. 6A and 6B are respectively a front view and a side viewschematically illustrating the configuration of a cell pack assemblingdevice;

FIG. 7 is a process diagram illustrating a method for disassembling acell pack according to one embodiment;

FIG. 8 is a front view schematically illustrating a cell pack accordingto another embodiment;

FIG. 9 is a side view schematically illustrating the cell pack of FIG.8;

FIGS. 10A and 10B are respectively a side view and a front viewschematically illustrating the configuration of a restraining hoopportion;

FIG. 11 is a process diagram illustrating a method for producing thecell pack according to another embodiment;

FIG. 12 is a process diagram illustrating a method for disassembling thecell pack according to another embodiment; and

FIGS. 13A and 13B are respectively a side view and a front viewschematically illustrating a conventional cell pack.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described.Incidentally, matters other than those particularly mentioned in thepresent specification and necessary for the implementation of thepresent disclosure (for example, the configuration of a unit cell notcharacterizing the present disclosure) are based on the related art inthe pertinent field and can be understood as design matters for a personskilled in the art. The present disclosure can be carried out based onthe contents disclosed in this specification and technical common sensein the field. In the specification, the numerical range expressed as “Ato B” means “A or more and B or less”.

In addition, in the following drawings, the same reference numerals areattached to members and parts that exhibit the same action. In thedrawings, reference symbols U, D, F, Rr, L, R respectively mean upward,downward, forward, rearward, leftward, and rightward. Reference symbolsX, Y, and Z in the drawings respectively denote a width direction, alongitudinal direction, and an arrangement direction of unit cells, Z1denotes a first direction in the arrangement direction Z, and Z2 denotesa second direction, which is opposite to the first direction Z1, in thearrangement direction Z. However, these are merely for convenience ofexplanation, and do not limit the installation, use mode, method forproducing, method for disassembling and the like of the cell pack atall.

First Embodiment

Battery Pack

FIG. 1 is a front view schematically illustrating a cell pack 1according to one embodiment, and FIG. 2 is a side view thereof. The cellpack 1 includes a plurality of unit cells 10 and a restraint mechanism20. The plurality of unit cells 10 are arranged in the predeterminedarrangement direction Z. The restraint mechanism 20 is a member forrestraining these unit cells 10 so that they can be treated as a cellpack. Each element will be described below.

Unit Cell

FIG. 3 is three-view diagrams consisting of a plan view (a), a frontview (b), and a side view (c) schematically illustrating the unit cell10. The unit cell 10 is typically a secondary cell that can berepeatedly charged and discharged, for example, a lithium ion secondarycell, a nickel metal hydride cell, an electric double layer capacitor,or the like. All-solid cells using a solid electrolyte composed ofceramics, ion conductive polymers or the like and using no flammableelectrolytic solution as an electrolyte have been put to practical usein order to improve safety of secondary cells. Hereinafter, theconfiguration where the unit cell 10 is an all-solid lithium ionsecondary cell will be described as an example, but the configuration ofthe unit cell 10 is not limited thereto. The unit cell 10 typicallyincludes a power generating element 14 including a positive electrode, anegative electrode, and a solid electrolyte (not shown) and a cell case12. One unit cell 10 may have only one power generating element 14 ortwo or more power generating elements. In this regard, the term “unitcell” as used in the present specification is a “battery module” definedin HS D 0114:2000, and the term “power generating element” as used inthe present specification means “unit cell” as defined in the samestandard. The power generating element 14 is accommodated in the cellcase 12.

In the all-solid state cell, the power generating element 14 isconfigured by arranging the solid electrolyte in a layer form between apositive electrode active material layer and a negative electrode activematerial layer. The solid electrolyte layer and the positive andnegative active material layers may be formed as a dense bulk body by,for example, a CVD method, or by binding a powdery (particulate)electrode constituting materials with a binder. Since an electrolyticsolution is not present in the all-solid state cell, the interfacialresistance between the solid electrolyte layer and the positive andnegative active material layers is higher than in a liquid-typesecondary cell including the electrolytic solution. In addition, theinterface resistance also occurs between particles constituting thesolid electrolyte layer and the positive and negative active materiallayers in an all-solid state cell produced using a powder material.Therefore, for cell packs made of all-solid state cells, it is requiredto apply a restraining pressure as high as about 5 to 10 times that ofcell packs of liquid type secondary cells for the purpose of reducingthe interfacial resistance. As will be described hereinbelow, in thecell pack 1 disclosed herein, the unit cells 10 can be restrained byconfining a higher restraining pressure than in the related art.Therefore, a power generating element formed using powdery electrodeconstituent material which requires the application of a higherrestraining pressure can be suitably used as the power generatingelement 14.

The solid electrolyte layer mainly includes a solid electrolytematerial. As the solid electrolyte material, for example, variouscompounds which have lithium ion conductivity but do not exhibitelectron conductivity can be suitably used. Specific examples of such asolid electrolyte materials include amorphous sulfides such asLi₂S—SiS₂, LiI—Li₂S—SiS₂, LiI—Li₂S—P₂S₅, LiI—Li₂S—B₂S₃,Li₃PO₄—Li₂S—Si₂S, Li₃PO₄—Li₂S—SiS₂, LiPO₄—Li₂S—SiS, LiI—Li₂S—P₂O₅,LiI—Li₃PO₄—P₂S₅, LiI—Li₃PS₄—LiBr, Li₂S—P₂S₅, Li₂S—P₂S₅—LiI—LiBr, andLi₂S—P₂S₅GeS₂ and the like, amorphous oxides such as Li₂O—B₂O₃—P₂O₅,Li₂O—SiO₂, Li₂O—B₂O₃, Li₂O—B₂O₃—ZnO and the like, crystalline sulfidessuch as Li₁₀GeP₂S₁₂ and the like, crystalline oxides such asLi_(1.3)Al_(0.3)Ti_(0.7)(PO₄)₃, Li_(1+x+y)A¹_(x)Ti_(2-x)Si_(y)P_(3-y)O₁₂ (A¹ is Al or Ga, 0≤x≤0.4, 0<y≤0.6), [(A²_(1/2)Li_(1/2))_(1-z)C_(z)]TiO₃ (A² is La, Pr, Nd, or Sm, C is Sr or Ba,0≤z≤0.5), Li₅La₃Ta₂O₁₂, Li₇La₃Zr₂O₁₂, Li₆BaLa₂Ta₂O₁₂, andLi_(3.6)Si_(0.6)P_(0.4)O₄ and the like, crystalline oxynitrides such asLi₃PO_((4-3/2w)) N_(w) (w<1) and the like, crystalline nitrides such asLi₃N and the like, and crystalline iodide such as LiI, LiI—Al₂O₃,Li₃N—LiI—LiOH and the like. Among them, amorphous sulfides can bepreferably used from the viewpoint of having excellent lithium ionconductivity.

A semi-solid polymer electrolyte such as polyethylene oxide,polypropylene oxide, polyvinylidene fluoride, or polyacrylonitrileincluding a lithium salt can also be used as a solid electrolyte.

Further, in the present specification, the expression “mainly includes”means that the component is included at 50% by mass or more, preferably60% by mass or more, more preferably 70% by mass or more, for example,at 80% by mass or more.

The positive electrode active material layer mainly includes a positiveelectrode active material. The negative electrode active material layermainly includes a negative electrode active material. As the positiveelectrode active material and the negative electrode active material,various materials usable as electrode active materials for all-solidstate cells can be used. For example, various compounds capable ofoccluding/releasing lithium ions can be suitably used. There is nospecific limitation on the positive electrode active material and thenegative electrode active material. For example, where thecharging/discharging potentials of two kinds of active materials arecompared, a material exhibiting a relatively noble charge/dischargepotential can be used for the positive electrode, and a materialexhibiting a low potential can be used for the negative electrode.

Examples of such active materials include lithium transition metaloxides of a layered rock salt type such as a lithium cobalt oxide (forexample, LiCoO₂), a lithium nickel oxide (for example, LiNiO₂),Li_(1+x)Co_(1/3)Ni_(1/3)Mn_(1/3)O₂ (x satisfies 0≤x<1) and the like,spinel-type lithium transition metal oxides such as lithium manganeseoxide (for example, LiMn₂O₄), Li—Mn spinets substituted with differentelements and having the composition represented by LI_(1+x)Mn_(2-x-y)M¹_(y)O₄ (M¹ is at least one metal element selected from the groupconsisting of Al, Mg, Ti, Co, Fe, Ni, and Zn; and x and y independentlysatisfy 0≤x, y≤1) and the like, oxides such as lithium titanium oxide(for example, Li_(x)TiO_(y), x and y independently satisfy 0≤x, y≤1),metallic lithium phosphate (for example, LiM²PO₄, M² is Fe, Mn, Co, orNi), vanadium oxide (for example V₂O₅), molybdenum oxide (for exampleMoO₃) and the like, titanium sulfide (for example, TiS₂), carbonmaterials such as graphite, hard carbon and the like, lithium cobaltnitride (for example, LiCoN), lithium silicon oxide (for example,Li_(x)Si_(y)O_(z), x, y, z independently satisfy 0≤x, y, z≤1), lithiummetal (Li), silicon (Si) and tin (Sn) and oxides thereof (for example,SiO, SnO₂), lithium alloys (for example, LiM³, where M³ is C, Sn, Si,Al, Ge, Sb, Pb or P), intermetallic compounds capable of storing lithium(for example, Mg_(x)M⁴ and M⁵ _(y)Sb, M⁴ is Sn, Ge, or Sb, M⁵ is In, Cu,or Mn), and derivatives and complexes thereof.

The electrode active material can undergo volume expansion/contractionas lithium ions are occluded/released. Here, the active material layermade of a material having a large volume change rate due toocclusion/release of lithium ions is likely to crack and peel off, andthe interface resistance is likely to increase. Meanwhile, since thecell pack 1 disclosed herein can be configured by confining arestraining pressure higher than that in the related art, as mentionedhereinabove, the increase in interfacial resistance caused by crackingor peeling of the active material layer or the like can be suitablysuppressed. From such a viewpoint, according to the technique disclosedherein, even a material having a large volume expansion coefficient canbe advantageously used as the electrode active material. As such anelectrode active material, for example, a carbon material or a metalmaterial that forms an alloy with lithium can be mentioned. Among them,metal materials such as silicon and silicon alloys, lithium and lithiumalloys, tin and tin alloys and the like having a high theoreticalcapacity can be advantageously used as the negative electrode activematerial.

In addition, in order to enhance the lithium ion conductivity in thepositive and negative active material layers, a part of the activematerial may be replaced with the above-mentioned solid electrolytematerial. In this case, the proportion of the solid electrolyte materialto be contained in the active material layer can be, for example, 60% bymass or less, preferably 50% by mass or less, and even more preferably40% by mass or less when the total content of the active material andthe solid electrolyte material is 100% by mass. Further, the proportionof the solid electrolyte material at the time of replacement is suitably10% by mass or more, preferably 20% by mass or more, and more preferably30% by mass or more. When performing such a replacement of the activematerial with the solid electrolyte material, the positive and negativematerial layers can be mainly composed of the active material and thesolid electrolyte material.

When a solid electrolyte composed of a sulfide is included in a positiveelectrode active material layer having a higher potential, a reactionlayer with a high resistance is formed at the interface between thepositive electrode active material and the solid electrolyte, and thereis a possibility of a high interface resistance. Therefore, in order tosuppress such an event, the positive electrode active material particlescan be coated with a crystalline oxide having lithium ion conductivity.The lithium ion conductive oxide for coating the positive electrodeactive material can be exemplified by an oxide represented by thegeneral formula LixA³Oy. In the formula, A³ is B, C, Al, Si, P, S, Ti,Zr, Nb, Mo, Ta or W, and x and y are positive numbers. Specific examplesof the lithium ion conductive oxide include Li₃BO₃, LiBO₂, Li₂CO₃,LiAlO₂, Li₄SiO₄, Li₂SiO₃, Li₃PO₄, Li₂SO₄, Li₂TiO₃, Li₄Ti₅O₁₂, Li₂Ti₂O₅,Li₂ZrO₃, LiNbO₃, Li₂MoO₄, Li₂WO₄ and the like. Further, the lithium ionconductive oxide may be a composite oxide composed of any combination ofthe above lithium ion conductive oxides, such as Li₄SiO₄—Li₃BO₃,Li₄SiO₄—Li₃PO₄ and the like.

When the surface of the positive electrode active material particles iscoated with the ion conductive oxide, at least a part of the positiveelectrode active material or the entire surface of the positiveelectrode active material particles may be coated with the ionconductive oxide. The thickness of the ion conductive oxide coating thepositive electrode active material particles is preferably, for example,0.1 nm or more, and more preferably 1 nm or more. Further, the thicknessof the ion conductive oxide is preferably, for example, 100 nm or less,and more preferably 20 nm or less. The thickness of the ion conductiveoxide can be measured, for example, using an electron microscope such asa transmission electron microscope (TEM).

The positive and negative active material layers may include, asnecessary, a conductive material for enhancing the electronconductivity. Examples of the conductive material include, but are notspecifically limited to, graphite, carbon black such as acetylene black(AB), Ketjen black (KB) and the like, vapor grown carbon fibers (VGCF),carbon nanotubes, carbon nanofibers, and other carbon materials can besuitably used. Such a conductive material may be included, for example,at 1% by mass or more, in the range of 1% by mass to 12% by mass,preferably 2% by mass to 10% by mass, based on 100% by mass of the totalamount of the electrode active material layer.

When the power generating element 14 is formed using a powdery electrodeconstituent material, the average particle diameter (D₅₀) thereof is notparticularly limited, and for example, it is preferable to use thefollowing size. That is, when the solid electrolyte layer is made of apowder material, the average particle diameter is, for example, about0.1 μm or more, preferably 0.4 μm or more. Further, the average particlediameter of the solid electrolyte material can be, for example, 50 μm orless, preferably 5 μm or less. When the electrode active material layeris made of a powder material, the average particle diameter is, forexample, 0.1 μm or more, and may be 0.5 μm or more. Meanwhile, theaverage particle diameter is, for example, 50 μm or less and may be 5 μmor less. When the powder material is processed into the form ofgranulated powder, the average particle diameter as the diameter ofprimary particles is preferably within the above range.

In this specification, the average particle diameter is a particlediameter corresponding to cumulative 50% in the volume-based particlesize distribution measured using a laser diffraction-light scatteringtype particle size distribution meter. For finer powders having anaverage particle diameter of 1 μm or less, measured values by thedynamic light scattering (DLS) method may be used.

There is also no particular limitation on the binder for binding thepowdery electrode constituent material. For example, various organiccompounds having binding properties can be used. Examples of suchbinders include polytetrafluoroethylene, polytrifluoroethylene,polyethylene, cellulose resin, acrylic resin, vinyl resin, nitrilerubber, polybutadiene rubber, butyl rubber, polystyrene, styrenebutadiene rubber, styrene butadiene latex, polysulfide rubber,acrylonitrile butadiene rubber, polyvinyl fluoride, polyvinylidenefluoride (PVDF), fluororubber, and the like. Any one of theabove-mentioned binders may be used singly, or two or more binders maybe used in combination as the binder.

The power generating element 14 is provided with a current collector, sothat electric power can be taken out to an external load. The shape ofthe current collector is not particularly limited, and examples ofsuitable shape include a foil, a plate, a mesh or the like. Further, forexample, an active material layer may be provided on the surface (oneside or both sides) of the current collector. Various materials whichare excellent in electron conductivity and are unlikely to be modifiedby the charge/discharge potential of the active material to be used aresuitable as such collectors. Examples of the current collector materialinclude aluminum, copper, nickel, iron, titanium, alloys thereof (forexample, an aluminum alloy, stainless steel), carbon and the like. Thethickness of the current collector is not particularly limited, becauseit depends on the size of the electrode body and the like, and ispreferably 5 μm or more and 500 μm or less, and more preferably 10 μm ormore and 100 μm or less.

When the unit cell 10 includes only one power generating element 14, forexample, the active material layer may be provided on one side of thecurrent collector. In this case, the power generating element 14 can beconstructed, for example, by laminating a positive electrode having apositive electrode active material layer on one side of a positiveelectrode current collector and a negative electrode having a negativeelectrode active material layer on one side of a negative electrodecurrent collector, with a solid electrolyte layer interposedtherebetween, with orientation such that the active material layers faceeach other. When the unit cell 10 includes two or more power generatingelements 14, for example, an active material layer may be provided onboth surfaces of the current collector. In this case, for example, aplurality of power generating elements 14 can be constructed bypreparing a plurality of positive electrodes having positive electrodeactive material layers on both surfaces of a positive electrode currentcollector and a plurality of negative electrodes having negativeelectrode active material layers on both surfaces of a negativeelectrode current collector and alternately laminating the positiveelectrodes and the negative electrodes so that the positive and negativeactive material layers are insulated from each other by a solidelectrolyte layer.

The interface resistance between the solid electrolyte layer and thepositive and negative active material layers is increased because noelectrolytic solution is present in the all-solid state cell. Inaddition, for example, in an all-solid state cell produced using apowdery material, interfacial resistance is increased by interfacesbetween particles, voids and the like also in the solid electrolytelayer and positive and negative active material layers. An effectivemethod of reducing such interfacial resistance is to increase thepacking density by applying pressure in the direction of compressing thepower generating element 14, in which the positive electrode activematerial layer, the solid electrolyte layer and the negative electrodeactive material layer are laminated, along the lamination directionthereof and reducing the voids between the layers and inside the layers.

Accordingly, in the present embodiment, the cell case 12 is configuredof a soft metal laminated film. The cell case 12 is an exterior materialfor housing the power generating element 14. The metal laminated film isconfigured by bonding a lightweight relatively soft metal foil such asaluminum or copper and an insulating thermoplastic resin sheet such aspolypropylene (PP), and has a high degree of freedom of deformation.Therefore, with the cell case 12 composed of the metal laminated film,the restraining pressure created by the restraint mechanism 20 can beeffectively applied to the power generating element 14, as compared withthe configuration where a cell case made of a metal can is used. Inaddition, by configuring the cell case 12 of a metal laminated film, itis possible to reduce the thickness and weight of the unit cell 10. Withthe cell case 12, for example, the power generating element 14 can beaccommodated in a bag made of, for example, a metal laminated film(typically, an aluminum/PP laminated sheet), and the bag can be sealedby thermal welding, thereby shielding the power generating element 14from the external environment. At this time, a positive electrodeterminal 16 a and a negative electrode terminal 16 b as externalconnection terminals 16 are drawn out of the cell case 12. The positiveelectrode terminal 16 a is electrically connected to the positiveelectrode current collector of the power generating element 14, and thenegative electrode terminal 16 b is electrically connected to thenegative electrode current collector of the power generating element 14.However, the cell case 12 is not limited to the one made of a metallaminated film, and may be a container made of aluminum, steel,high-strength plastic, or the like and having a square shape, acylindrical shape, or the like.

As shown in FIG. 3(a) to (c), the unit cell 10 includes a rectangularplate-shaped power generating element 14 that is elongated in thelongitudinal direction Y in a plan view. In the power generating element14, a positive electrode active material layer, a solid electrolytelayer, and a negative electrode active material layer, each of arectangular shape in a plan view, are laminated in the thicknessdirection. The cell case 12 that houses the power generating element 14is also a rectangle elongated in the longitudinal direction Y in a planview. In the portion of the cell case 12 where the power generatingelement 14 is not present, the metal laminated film is welded, and thethickness (dimension in the arrangement direction Z) in a front view anda side view is small. An external connection terminal 16 is disposed soas to protrude from an end portion of the front side F of the cell case12 in the longitudinal direction Y. The positive electrode terminal 16 aand the negative electrode terminal 16 b of the external connectionterminal 16 are arranged apart from each other in the width direction X.A plurality of such unit cells 10 is arranged and stacked in such amanner that the thickness direction of the power generating elements 14is in the arrangement direction Z. As a result, a cell stack composed ofa plurality of arranged unit cells is configured.

Restraint Mechanism

The restraint mechanism 20 includes a pair of end plate portions 21, 22and a restraining hoop portion 24. The end plate portions 21, 22 areplate-shaped members for uniformly applying a restraining pressure tothe power generating elements 14 of the unit cells 10. The restraininghoop portion 24 is a member by which the restraining pressure appliedbetween the end plate portions 21, 22 is confined and maintained betweenthe end plate portions 21, 22.

The pair of end plate portions 21, 22 are disposed at both ends of thearranged plurality of unit cells 10 so as to sandwich the arranged unitcells 10 in the arrangement direction Z. The first end plate portion 21is disposed at the end portion in a first direction Z1 (upper side U) ofthe arrangement direction Z of the arranged unit cells 10. The secondend plate portion 22 is arranged at the end portion in a seconddirection Z2 (lower side D) of the arrangement direction Z of thearranged unit cells 10. The end plate portions 21, 22 are disposed to beperpendicular to the arrangement direction Z so that the end plateportions are parallel to each other. The size of the end plate portions21, 22 in the width direction X is slightly larger than the size of thecell case 12 of the unit cell 10. The size of the end plate portions 21,22 in the longitudinal direction Y is slightly larger than the size ofthe power generating element 14 of the unit cell 10. The end plateportions 21, 22 are configured to be slightly larger than the powergenerating element 14 of the unit cell 10. Further, in the front view ofthe first end plate portion 21, right and left corner portions in thewidth direction X on the upper U side are rounded and curved. In thefront view of the second end plate portion 22, right and left cornerportions in the width direction X on the lower side D are rounded andcurved.

The restraining hoop portion 24 has a ring-shaped belt form. Therestraining hoop portion 24 has an upper surface portion 24U disposed onthe upper side U along the surface of the upper side U of the first endplate portion 21. The restraining hoop portion 24 has a lower surfaceportion 24D disposed on the lower side D along the surface of the lowerside D of the second end plate portion 22. In the restraining hoopportion 24, a flat left side surface portion 24L continuously connectingthe upper surface portion 24U and the lower surface portion 24D alongthe arrangement direction Z is provided on the left side L so as toextend from the left end of the first end plate portion 21 to the leftend of the second end plate portion 22. In the restraining hoop portion24, a flat right surface portion 24R continuously connecting the uppersurface portion 24U and the lower surface portion 24D along thearrangement direction Z is provided on the right side R so as to extendfrom the right end of the first end plate portion 21 to the right end ofthe second end plate portion 22. As a result, in the cross sectionparallel to the arrangement direction Z and the width direction X, therestraining hoop portion 24 annularly surrounds the stack composed ofthe first end plate portion 21, the arranged plurality of unit cells 10and the second end plate portion 22 along the outer periphery of thestack. In the present embodiment, the restraint mechanism 20 includes atotal of two restraining hoop portions 24, one on the front side F andthe other on the rear side Rr in the longitudinal direction Y of the endplate portions 21, 22. The upper surface portion 24U and the lowersurface portion 24D are examples of the first support portion and thesecond support portion in the cell pack 1 disclosed herein.

As shown in FIG. 4E, jig holes 21 a, 22 a penetrating in the widthdirection X are provided in the end plate portions 21, 22, respectively,near the center in the thickness direction. The jig holes 21 a, 22 a areholes for inserting mounting jigs 55 u, 55 d (see FIGS. 6A and 6B) usedin the below-described production and disassembling of the cell pack 1into the end plate portions 21, 22 and passing the jigs therethrough. Atotal of three jig holes 21 a, 22 a are provided, one on the front sideF, one on the rear side Er, and one in the center in the longitudinaldirection Y. The jig holes 21 a and 22 a are provided at equal intervalsalong the longitudinal direction Y so as to be disposed at both ends ofthe two restraining hoop portions 24 and in the middle thereof. However,these number, placement and the like of the jig holes 21 a, 22 a are notlimiting.

Since the restraining hoop portion 24 is closed in a ring shape, theseparation distance of the end plate portions 21, 22 is regulated. Thedimension, in the arrangement direction Z, of the left side surfaceportion 24L and the right side surface portion 24R of the restraininghoop portion 24 is equal to the dimension, in the arrangement directionZ, of the plurality of unit cells 10 restrained in the arranged state.As a result, in the restraining hoop portion 24, the dimension of theleft side surface portion 24L and the right side surface portion 24R inthe arrangement direction Z are determined so that the restrainingpressure applied to the unit cell 10 has a predetermined value. Forexample, as a result of making the dimension of the left side surfaceportion 24L and the right side surface portion 24R in the arrangementdirection Z less than the dimension of the cell stack in an unloadedstate in the arrangement direction Z, the restraining hoop portion 24can confine the restraining pressure applied to the unit cells 10 andrestrain the cell stack. Further, in the restraining hoop portion 24,the dimension of the left side surface portion 24L and the right sidesurface portion 24R in the arrangement direction Z is determined so thatthe reaction force from the cell stack acting against the restrainingpressure does not result in yield. In other words, for example, sincethe restraining hoop portion 24 is deformed in the elastic region in thetensile direction along the arrangement direction Z, a high restrainingpressure acting in the compression direction with respect to the unitcell 10 can be confined. The restraining pressure applied to the unitcell 10 is maintained by the restraining hoop portion 24. Therestraining hoop portion 24 is configured so as to be able to maintainan unprecedentedly high restraining pressure of, for example, about 0.1MPa to 110 MPa, with respect to the unit cell 10. The restrainingpressure may be, for example, 1 MPa or more, 10 MPa or more, 30 MPa ormore, 50 MPa or more, 80 MPa or more, and 100 MPa or more. The loadapplied to the long side surface of the unit cell 10 can be increasedaccording to the tensile strength of the restraining hoop portion 24 toan unprecedented value, for example, 2 t or more, 5 t or more, 8 t ormore, and 10 t or more. Since the corner portions of the end plateportions 21, 22 (the corner portions from the outer surface on the sideopposite to the unit cells 10 in the arrangement direction Z to the sidesurface in the width direction X) are curved, the restraining pressureis prevented from locally acting on the restraining hoop portion 24.

The end plate portions 21, 22 can be made of various materials that arenot deformed by the restraining pressure applied to the unit cells 10along the arrangement direction Z. Examples of the constituent materialof the end plate portions 21, 22 include metal materials typified byaluminum or an aluminum alloy, iron or various steel materials (forexample, structural steel), high-strength alloys and the like, resinmaterials such as reinforced plastics, engineering plastics and thelike, inorganic materials having high flexural strength such as fineceramics, carbon fiber materials and the like, and composite materialsthereof such as carbon fiber reinforced plastics (CFRP) and the like. Inaddition, the restraining hoop portion 24 can be made of variousmaterials having a tensile strength such that the reaction force fromthe unit cells 10 against the restraining force in the arrangementdirection Z does not cause plastic deformation (stretching) such thatexceeds the yield point or breaking. Examples of such a hoopconstituting material include metal materials typified by aluminum or analuminum alloy, iron or various steel materials (for example, structuralsteel), high-strength alloys and the like, resin materials such asreinforced plastics, engineering plastics and the like, inorganicmaterials having high tensile strength such as carbon fiber materialsand the like, and composite materials thereof such as carbon fiberreinforced plastics (CFRP) and the like.

As an example, as shown in FIGS. 4A and 4D, the restraining hoop portion24 has a seamless ring-shaped structure made of a single material. Sucha restraining hoop portion 24 can be produced by using variousconventionally known methods. When the hoop constituting material is aresin material, a seamless tubular resin hoop can be obtained by, forexample, an injection molding method, a casting method or the like. Whenthe hoop constituting material is a metal material, a seamless tubularmetal hoop can be obtained by, for example, a cutting method, acentrifugal casting method, piercing rolling, or the like. When the hoopconstituting material is a resin material or a metal material, a tubularclosed resin hoop or metal hoop can be obtained, for example, by bendinga sheet-shaped hoop constituting material into a tubular shapecorresponding to the cross sectional shape of the restraining hoopportion and then solid-bonding the end portions. Furthermore, when thehoop constituting material is CFRP, a tubular CFRP hoop can be obtainedby, for example, annularly winding a prepreg sheet composed of a carbonfiber and a parent phase resin material such as an epoxy resin around ametal mold corresponding to the cross-sectional shape of the restraininghoop portion and integrating by heating. The restraining hoop portions24 can be obtained by cutting these tubular hoops to a desired hoopwidth. As a result of increasing the width of the restraining hoopportion 24, the restraining hoop portion 24 can enclose a higherrestraining pressure.

Meanwhile, as an example, the restraining hoop portion 24 may have aseamed ring-shaped structure as shown in FIGS. 4B and 4C. When therestraining hoop portion 24 has seams, in order to equalize the tensilestrength between the left side surface portion 24L and the right sidesurface portion 24R of the restraining hoop portion 24, seams arepreferably provided on the left side surface portion 24L and the rightside surface portion 24R. Such a restraining hoop portion 24 can beformed, for example, by overlapping and joining end portions of twomembers which are U-shaped (semi-annular) when viewed from the front.Examples of joining methods include a method of joining via a joiningmaterial such as an adhesive, as shown in FIG. 4B, and methods fordirect joining which do not use a joining material, such as a laserwelding method, a resistance welding method, a solid phase bondingmethod, or the like (see FIG. 4C).

Here, for example, when two U-shaped members are overlapped and joinedto form a ring, a vector of tensile stress acting on the restraininghoop portion 24 is slightly shifted in the width direction X at theU-shaped one member and another member. When the restraining pressurefor restraining the unit cell 10 is small, such a shift in the vector oftensile stress causes no problem, but where the restraining pressurerises to a level that has not been heretofore reached (typically, about5 times or more, for example, about 10 times or more of the level usedin the related art), the restraining hoop portion 24 sometimes deformsthe joining portion in the direction of correcting the shift of thevector of tensile stress. As a result, the tensile stress acting on therestraining hoop portion 24 tends to locally concentrate at, forexample, the upper or lower end of the joining portion, and the U-shapedone member and other member can be broken starting from the upper orlower end of the joining portion. From such a viewpoint, it is morepreferable that the restraining hoop portion 24 have a seamless ringshape as shown in FIGS. 4A and 4D.

The dimension of the restraining hoop portion 24 in the hoop widthdirection corresponding to the longitudinal direction Y is notparticularly limited. For example, the total dimension of one or aplurality of restraining hoop portions 24 in the hoop width directionmay be ¼ or more of the dimension of the power generating element 14 inthe longitudinal direction Y (that is, in the hoop width direction). Forexample, when the restraint mechanism 20 is provided with tworestraining hoop portions 24, the dimension of each of the restraininghoop portions 24 in the hoop width direction may be ⅛ or more of thedimension of the power generating element in the hoop width direction.As a result, the plurality of unit cells 10 can be stably restrained bythe restraint mechanism 20. The total dimension of the restraining hoopportion 24 in the hoop width direction may be ⅓ or more, preferably ½ ormore, more preferably ⅔ or more, and may be ¾ or more, or ⅚ or more ofthe dimension of the power generating element in the longitudinaldirection Y. The total dimension of the restraining hoop portion 24 inthe hoop width direction can be set to, for example, 1.1 or less and maybe 1 or less and 0.9 or less of the dimension of the power generatingelement 14 in the longitudinal direction Y to ensure the balance betweenthe assembling accuracy and cost reduction. When the dimension of thehoop width of the restraining hoop portion 24 is ½ or more of thedimension of the power generating element 14 in the longitudinaldirection Y, the restraint mechanism 20 may be provided with only onesuch a wide restraining hoop portion 24. With such a configuration aswell, the plurality of unit cells 10 can be stably restrained by therestraint mechanism 20.

With such a configuration, the restraint mechanism 20 surrounds theouter peripheries of the pair of end plate portions 21, 22 by thering-shaped restraining hoop portion 24, thereby restraining theplurality of unit cells 10 in the direction of compressing along thearrangement direction Z. In the restraint mechanism 20, the restraininghoop portion 24 is not fixed by using a separate member such as afastener. Therefore, the restraint mechanism 20 includes no fastenerthat can be plastically deformed or broken, the restraint of the unitcells 10 can be prevented from loosening and the restraining pressurenecessary for the unit cells 10 can be maintained for a long period.This can be particularly effective, for example, in the cell pack 1 inwhich vibration, impact or the like occurs during use. Further, such aneffect is particularly advantageously demonstrated with the cell pack 1which requires an unprecedentedly high restraining pressure, forexample, when the unit cell 10 is an all-solid state cell for which theapplication of compressive stress is desirable in order to reduce theinterfacial resistance or when a material having a large volumeexpansion rate in charging and discharging is used as the activematerial.

Production Method 1

The cell pack 1 having the above configuration can be suitably produced,as shown, for example, in FIG. 5, by following the production steps S1to S5 described hereinbelow.

-   (S1) Preparing a cell stack S_(A)-   (S2) disposing the first end plate portion 21, the second end plate    portion 22 and the restraining hoop portion 24-   (S3) stretching the restraining hoop portion 24-   (S4) inserting the cell stack S_(A) between the end plate portions    21, 22-   (S5) restraining the plurality of unit cells 10

Such a method for producing the cell pack 1 can be suitably implemented,for example, by using a cell pack assembling device 50 shown in FIGS. 6Aand 6B. That is, the cell pack assembling device 50 includes, as maincomponents, a base portion 51, a top plate portion 52, and fourhydraulic pistons 53. The hydraulic pistons 53 are erected at fourcorners of the base portion 51 so that the central axis thereof extendsalong the vertical direction. The vertical direction coincides with thearrangement direction Z of the cell pack 1. The hydraulic pistons 53fixedly support the four corners of the top plate portion 52 from thelower side D. The hydraulic pistons 53 are configured so that thedistance between the base portion 51 and the top plate portion 52 can bearbitrarily changed by vertically moving the top plate portion 52 alongthe vertical direction.

A pair of end plate holders 54 u for fixing the first end plate portion21 to the top plate portion 52 is provided so as to face each other onthe lower surface of the top plate portion 52. A pair of end plateholders 54 d for fixing the second end plate portion 22 to the baseportion 51 is provided so as to face each other on the upper surface ofthe base portion 51. In the pairs of the end plate holders 54 u, 54 d,through holes (not shown) are provided on the same axis along the widthdirection X. Bolt-nut type mounting jigs 55 u, 55 d are detachablyprovided in the opposing through holes of the end plate holders 54 u, 54d so as to communicate through the through holes. In the cell packassembling device 50 of the present embodiment, three through holes areprovided at equal intervals along the longitudinal direction Y in theend plate holders 54 u, 54 d. The positions of the through holesprovided in the end plate holders 54 u, 54 d and the jig holes 21 a, 22a provided in the end plate portions 21, 22 correspond to each other.

First, in the production step S1, as shown in FIG. 5, a plurality ofunit cells 10 is arranged such that the thickness direction is thearrangement direction Z. As a result, the cell stack S_(A) in which theplurality of unit cells 10 are arranged is prepared. Here, the pluralityof unit cells 10 are laminated by aligning the width direction X and thelongitudinal direction Y so that the power generating elements 14 towhich the compressive stress is to be applied are aligned in thearrangement direction Z. The dimension of the prepared cell stack S_(A)in the arrangement direction Z is B1. The cell stack S_(A) may bepreliminarily compressed by pressing in the arrangement direction Zbefore being inserted between the end plate portions 21, 22 in thesubsequent step.

In the production step S2, the first end plate portion 21 and the secondend plate portion 22 of the restraint mechanism 20 are arranged apartfrom each other along the arrangement direction Z, and the ring-shapedrestraining hoop portion 24 is disposed so as to surround the first endplate portion 21 and the second end plate portion 22 by planes parallelto the arrangement direction Z. At this time, the first end plateportion 21 may be inserted in advance into the ring of the restraininghoop portion 24, and in this state the first end plate portion 21 may befixed to the end plate holder 54 u of the cell pack assembling device50. When fixing to the end plate holder 54 u, the first end plateportion 21 may be disposed so that the position of the jig hole 21 a andthe position of the through hole are aligned on the same axis betweenthe pair of end plate holders 54 u, and the mounting jig 55 u may beinserted into the jig hole 21 a and the through hole and fixed with anut. Likewise, with respect to the second end plate portion 22, thesecond end plate portion 22 may be inserted in advance into the ring ofthe restraining hoop portion 24, and in this state the second end plateportion 22 may be fixed to the base portion 51. When fixing to the endplate holder 54 d, the second end plate portion 22 may be disposed sothat the position of the jig hole 22 a and the position of the throughhole are aligned on the same axis between the pair of end plate holders54 d, and the mounting jig 55 d may be inserted into the jig hole 22 aand the through hole and fixed with a nut. As a result, the restraintmechanism 20 can be set in the cell pack assembling device 50. Here, thedimension of the left side surface portion 24L and the right sidesurface portion 24R of the restraining hoop portion 24 along thearrangement direction Z is A1. The separation distance between the firstend plate portion 21 and the second end plate portion 22 is also A1. Thedimension A1 and the dimension B1 satisfy A1<B1. The dimension A1 isdetermined so as to substantially match the dimension when the cellstack S_(A) is compressed by a predetermined restraining pressure in thecell pack 1.

In the production step S3, the first end plate portion 21 is relativelydisplaced in the first direction Z1 on the side opposite to the secondend plate portion 22 in the arrangement direction Z. The degree ofdisplacement may be adjusted so that the separation distance between thefirst end plate portion 21 and the second end plate portion 22 is equalto or greater than the dimension B1 of the cell stack S_(A) in thearrangement direction Z. The hydraulic piston 53 of the cell packassembling device 50 may be driven to displace the first end plateportion 21. As a result, the restraining hoop portion 24 can bestretched in the arrangement direction Z. However, the degree ofdisplacement of the first end plate portion 21 is limited to the rangein which the restraining hoop portion 24 is extended in the elasticregion. In other words, the displacement amount of the first end plateportion 21 is determined so that the restraining hoop portion 24 doesnot undergo yield deformation due to stretching. The dimension B1 of thecell stack S_(A) in the arrangement direction Z is determined so thatthe dimension A1 of the left and right side surface portions 24L, 24R ofthe restraining hoop portion 24 along the arrangement direction Z canbecome the dimension B1 without causing the yield. In the cell packassembling device 50 disclosed herein, four hydraulic pistons 53 areused to displace the first end plate portion 21. This makes it possibleto control the stretching of the restraining hoop portion 24 having ahigh tensile strength with high accuracy.

In the production step S4, the cell stack S_(A) is inserted between thedisplaced first end plate portion 21 and the second end plate portion22. For example, the restraining hoop portion 24 is disposed so as toform a ring in a plane perpendicular to the longitudinal direction Y.Therefore, the cell stack S_(A) may be inserted between the first endplate portion 21 and the second end plate portion 22, for example, bysliding the cell stack disposed on the rear side Rr of the stretchedrestraining hoop portion 24 in the longitudinal direction Y to the frontside F. As a result, the cell stack S_(A) can be smoothly inserted intothe restraint mechanism 20.

In the production step S5, the displacement of the first end plateportion 21 is released. For example, the force maintaining thedisplacement of the first end plate portion 21 can be released byreleasing the pressure of the four hydraulic pistons 53. As aconsequence, the restraining hoop portion 24, which has been extendedelastically, contracts so as to return to the original dimension A1. Asa result, the first end plate portion 21 is relatively displaced towardthe second end plate portion 22. Thus, the first end plate portion 21,the second end plate portion 22, and the restraining hoop portion 24 canapply a load to the plurality of unit cells 10 in a direction ofcompressing along the arrangement direction Z. As a result, it ispossible to restrain the plurality of unit cells 10 in the arrangedstate. After releasing the pressure of the hydraulic piston 53, the cellpack 1 can be obtained by removing the mounting jigs 55 u, 55 d from theend plate holders 54 u, 54 d.

It should be noted that various inconveniences may occur when the cellpack 1 having the configuration disclosed herein is to be produced, forexample, by the same method as the method for producing a conventionalcell pack. For example, as shown in FIGS. 13A and 13B, in a conventionalcell pack 101, a cell stack composed of a plurality of unit cells 110 issandwiched between a pair of end plate portions 121, 122 and compressedunder a predetermined compressive stress, and in this state, aconventional U-shaped restraining band 124 is fixed to the end plateportions 121, 122. Here, with the conventional U-shaped restraining band124, a mounting space for the restraining band 124 can be ensured at theend portions of the end plate portions 121, 122 while uniformly pressingalmost all the surfaces of the end plate portions 121, 122 to compressthe unit cells 110. However, where the ring-shaped restraining hoopportion 24 is to be attached in place of the restraining band 124, it isnecessary to mount the restraining hoop portion 24 so as to extend overthe width direction X of the end plate portions 21, 22. Therefore, themounting space is difficult to ensure. For example, an attempt can bemade to mount the ring-shaped restraining hoop portion 24 on anon-pressing region, without pressing both end portions of the end plateportions 21, 22 in the longitudinal direction Y. In such a case, in thecell stack and the end plate portions, although the central portion inthe longitudinal direction Y is locally pressed, the non-pressing areais not pressed, so that the cell stack and the end plate portions aredeflected in the longitudinal direction Y and the end portions in thelongitudinal direction Y expand outside in the arrangement direction Z.As a result, the size of the ring-shaped opening of the restraining hoopportion 24 becomes relatively small, and it is impossible to insert theend portions of the expanded cell stack S_(A) and the end plate portions21, 22.

By contrast, according to the method disclosed herein, a gap forinserting the cell stack SA between the end plate portions 21, 22 isappropriately ensured by elastically deforming the restraining hoopportion 24 by pulling. As a result, the ring-shaped restraining hoopportion 24 can be fitted to the outer peripheries of the pair of endplate portions 21, 22, and the end plate portions 21, 22 and the cellstack S_(A) can be bundled by the restraining hoop portion 24.

Disassembling Method 1

With the cell pack 1 enclosing a high restraining pressure, as describedabove, where the restraining pressure is abruptly released at the timeof disassembling, there is a danger that the cell stack S_(A) or therestraint mechanism 20 will be scattered violently to the surroundings.Here, the above-described cell pack assembling device 50 can also besuitably used for disassembling the cell pack 1, for example, as shownin FIG. 7, by following the disassembling steps S101 to S104 describedbelow.

That is, in the disassembling step S101, the cell pack 1 is set in thecell pack assembling device 50. Specifically, first, the first end plateportion 21 of the cell pack 1 is fixed to the end plate holder 54 u ofthe cell pack assembling device 50. Here, the mounting jig 55 u isdetached in advance from the end plate holder 54 u. Next, the first endplate portion 21 may be disposed so that the position of the jig hole 21a and the position of the through hole are aligned on the same axisbetween the pair of end plate holders 54 u, and the mounting jig 55 umay be inserted into the jig hole 21 a and the through hole and fixedwith a nut. Next, the second end plate portion 22 is fixed to the baseportion 51. Here, likewise, the mounting jig 55 d is detached in advancefrom the end plate holder 54 d. Next, the second end plate portion 22 isdisposed so that the position of the jig hole 22 a and the position ofthe through hole are aligned on the same axis between the pair of endplate holders 54 d, and the mounting jig 55 d is inserted into the jighole 22 a and the through hole and fixed with a nut. When mounting thecell pack 1, the distance between the base portion 51 and the top plateportion 52 may be adjusted to a distance suitable for fixing the endplate portions 21, 22 of the cell pack 1 by adequately controlling thepressure of the hydraulic piston 53.

Next, in the disassembling step S102, the first end plate portion 21 isdisplaced relative to the second end plate portion 22 in the firstdirection Z1. The degree of displacement of the first end plate portion21 when disassembling the cell pack 1 may be in the range in which therestraining hoop portion 24 extends in the elastic region or in therange in which the restraining hoop portion 24 yields and plasticallydeforms. Here, where the restraining hoop portion 24 is plasticallydeformed, the restraining force confined in the restraining hoop portion24 can be released. However, from the viewpoint of safety, the degree ofdisplacement of the first end plate portion 21 is preferably such thatthe restraining hoop portion 24 does not break, and from the viewpointof efficient disassembling, the degree of displacement may be within therange in which the restraining hoop portion 24 extends in the elasticregion. In addition, it is preferable that the displacement of the firstend plate portion 21 be performed slowly in order to avoid a suddenrelease of the restraining pressure of the cell stack S_(A). As aresult, it is possible to release the restraining pressure from the cellstack S_(A) while preventing the cell stack S_(A) from scattering or thelike due to abrupt release of the restraining pressure. Further, it ispossible to secure a gap for taking out the cell stack S_(A) frombetween the first end plate portion 21 and the second end plate portion22.

In the disassembling step S103, the cell stack S_(A) is taken out frombetween the displaced first end plate portion 21 and the second endplate portion 22. For example, the restraining hoop portion 24 isdisposed so as to form a ring in a plane perpendicular to thelongitudinal direction Y. Therefore, the cell stack S_(A) may be takenout from between the first end plate portion 21 and the second end plateportion 22, for example, by sliding the cell stack disposed on the frontside F of the stretched restraining hoop portion 24 in the longitudinaldirection Y to the rear side Rr. As a result, the cell stack S_(A) canbe smoothly taken out from the restraint mechanism 20.

In the disassembling step S104, the displacement of the first end plateportion 21 is released. For example, the force maintaining thedisplacement of the first end plate portion 21 can be released byreleasing the pressure of the four hydraulic pistons 53. As aconsequence, although no change is observed with respect to therestraining hoop portion 24 which has been plastically deformed, therestraining hoop portion 24 which has been extended in the elasticregion elastically contracts to return to the original dimension. As aresult, the first end plate portion 21 is relatively displaced towardthe second end plate portion 22. Thus, it is possible to release therestraining pressure from the restraining hoop portion 24 confining therestraining pressure, and the cell pack 1 can be safely disassembled.

Second Embodiment

Restraint Mechanism

In the cell pack 1 of the first embodiment described above, therestraint mechanism 20 is provided with two restraining hoops 24. Themerits of the configuration disclosed herein is that where only onerestraining hoop portion 24 having a relatively large width in thelongitudinal direction Y is provided, as shown in FIG. 4D, in additionto reducing the number of parts, the end plate portions 21, 22 and thecell stack S_(A) can be restrained in a stable manner with a strongerrestraining force. Accordingly, with the restraint mechanism 20 of thepresent embodiment, the first end plate portion 21, the second end plateportion 22, and the restraining hoop portion 24 are integrally molded ofone material, for example, as shown in FIGS. 8, 9, 10A, and 10B. Inother words, the pair of end plate portions 21, 22 and the restraininghoop portion 24 are a single constituent member rather than acombination of a plurality of constituent members. In the cell pack 1 ofthe present embodiment, the configuration of the unit cell 10, that is,a component of the cell pack other than the restraint mechanism 20, isthe same as that of the above-described first embodiment, so duplicateexplanation will be omitted.

The widths of the first end plate portion 21, the second end plateportion 22 and the restraining hoop portion 24 in the longitudinaldirection Y are not necessarily the same. However, from the viewpoint ofstably maintaining a higher restraining pressure confined in therestraint mechanism 20, the widths of the first end plate portion 21,the second end plate portion 22 and the restraining hoop portion 24 inthe longitudinal direction Y may be substantially the same. In otherwords, the dimensions of the first end plate portion 21 and the secondend plate portion 22 in the longitudinal direction Y and the dimensionsof the left side surface portion 24L and the right side surface portion24R of the restraining hoop portion 24 in the longitudinal direction Yare preferably the same. The dimension of the restraint mechanism 20 inthe longitudinal direction Y is preferably slightly larger (for example,about 1 to 1.1 times or less) than the dimension of the power generatingelement 14 in the longitudinal direction Y. Further, the dimension ofthe restraint mechanism 20 in the longitudinal direction Y can be madesmaller than the dimension of the unit cell 10 in the longitudinaldirection Y. Since the constituent material of the restraint mechanism20 and the forming method thereof can be grasped by a person skilled inthe art in the same manner as in the first embodiment, duplicateexplanation will be omitted.

Production Method 2

The negative consequence of increasing the width of the restraining hoopportion 24 in the longitudinal direction Y is that the force requiredfor elastically deforming the restraining hoop portion 24 in the methodof producing the cell pack is greatly increased and the productivity ofthe cell pack 1 is poor. Therefore, the cell pack 1 having theconfiguration according to the second embodiment can be suitablyproduced by following the production steps S11 to S15, for example, asshown in FIG. 11.

-   (S11) preparing a cell stack S_(B) by arranging a plurality of unit    cells 10 and sliding plates 28, 29 in the arrangement direction Z-   (S12) compressing the cell stack S_(B) in the arrangement direction    Z-   (S13) installing the expansion suppressing jig 64 in the restraint    mechanism 20 including the first end plate portion 21, the second    end plate portion 22, and the ring-shaped restraining hoop portion    24-   (S14) inserting the cell stack S_(B) between the end plate portions    21, 22-   (S15) restraining the plurality of unit cells 10

Such a method for producing the cell pack 1 can be suitably implemented,for example, by using a cell pack assembling device 60 shown in FIG. 11.That is, the cell pack assembling device 60 includes a base portion 61,a top plate portion 62, a compressing portion 63, an expansionsuppressing jig 64, and a slider mechanism 65. The cell pack assemblingdevice 60 includes a housing including the base portion 61, the topplate portion 62, and left and right side walls standing on the baseportion 61 and supporting the top plate portion 62. The space inside thehousing includes a compression area on the rear side Rr and an assemblyarea on the front side F.

The compressing portion 63 is a mechanism for compressing the cell stackS_(B), and is disposed in the compression area on the rear side Rr. Thecompressing portion 63 is connected to four hydraulic pistons and thesehydraulic pistons are fixed to the four corners of the top plate portion62 of the compression area so that the central axis is along the heightdirection H in which the central axis coincides with the verticaldirection. The hydraulic pistons in the compression area move thecompressing portion 63 to the lower side D or the upper side U in theheight direction H, thereby making it possible to compress the object tobe compressed (here, the cell stack S_(B)) which is disposed on the baseportion 61 in the compression area or to release the compression. A loadcell (not shown) is disposed on the base portion 61 in the compressionarea and is configured to or programmed to be capable of detecting thecompression load applied by the compressing portion 63 to the object tobe compressed.

The expansion suppressing jig 64 is a mechanism for suppressing theexpansion of the restraining hoop portion 24 in the arrangementdirection Z, and is disposed in the assembly area on the front side F.The expansion suppressing jig 64 is connected to four hydraulic pistonsand these hydraulic pistons are fixed to the four corners of the topplate portion 62 in the assembly area so that the central axis is alongthe height direction H.

The slider mechanism 65 for slidably moving the cell stack S_(B) isprovided on a side wall on the rear side Rr of the housing. The slidermechanism 65 includes one hydraulic piston on each of the upper side Uand the lower side D. These hydraulic pistons are fixed to the side wallon the rear side Rr so that the central axis is along the longitudinaldirection Y coincident with the horizontal direction. The slidermechanism 65 is configured so that the position thereof in the heightdirection H can be adjusted so as to correspond to the height positionsof the sliding plates 28, 29 in the compressed cell stack S_(B)described hereinbelow. When the slider mechanism 65 is driven in theforward direction F along the longitudinal direction Y, the cell stackS_(B) arranged in the compression area can be slidably moved to theassembly area. On the base portion 61, spacers for adjusting theposition of the placed member in the height direction H are providedseparately for the compression area and the assembly area.

In step S11, the plurality of unit cells 10 is arranged in thearrangement direction Z, the first sliding plate 28 is disposed at theend portion in the first direction Z1 (upper side U) in the arrangementdirection Z of the plurality of unit cells 10, and the second slidingplate 29 is disposed at the end portion in the second direction Z2(lower side D). As a result, the cell stack S_(B) having a form in whichthe plurality of unit cells 10 is sandwiched between the sliding plates28, 29 in the arrangement direction Z is prepared.

Here, the sliding plates 28, 29 are plate-shaped members for sliding thecell stack S_(B) in the longitudinal direction Y while suppressing thefrictional resistance when inserting the cell stack S_(B) between theend plate portions 21, 22 in a subsequent process. Therefore, it ispreferable that the surfaces of the sliding plates 28, 29 which are incontact with the end plate portions 21, 22 have a low frictioncoefficient. In other words, it is preferable that the upper surface ofthe first sliding plate 28 and the lower surface of the second slidingplate 29 have a low friction coefficient. For the same reason, it ispreferable that the lower surface of the compressing portion 63 and theupper surface of the compression area of the base portion 61 (which maybe the upper surface of the spacer) have a low friction coefficient. Thefriction coefficients of the surfaces of the sliding plates 28, 29, thecompressing portion 63, and the base portion 61 may be independently 0.5or less, preferably 0.4 or less, and 0.3 or less. For example, 0.2 orless (typically, 0.20 or less) is particularly preferable. The frictioncoefficient of the surfaces of the sliding plates 28, 29 may be 0.15 orless (less than 0.15) or 0.1 or less. The sliding plates 28, 29 can beconfigured of, for example, a metal material having a smooth surface andtypified by aluminum or an aluminum alloy, iron or various steelmaterials (for example, structural steel), high-strength alloys and thelike, or a resin material such as a fluororesin, a reinforced plastic,an engineering plastic and the like. The sliding plates 28, 29 may besubjected to a surface treatment such as coating or polishing so as torealize the desired friction coefficient. The friction coefficient inthe present specification means a static friction coefficient (μ_(s)),and can be measured, for example, in accordance with JIS K 7125:1999.

It is preferable that the sliding plates 28, 29 have dimensions in thewidth direction X that are slightly larger than the dimensions of thepower generating elements 14 of the unit cells 10 and smaller than thedimensions of the end plate portions 21, 22. The dimension of thesliding plates 28, 29 in the longitudinal direction Y is slightly largerthan the dimension of the power generating elements 14 of the unit cells10, and can be set to be approximately the same, for example, as thedimension of the end plate portions 21, 22 in the longitudinal directionY. The sliding plates 28, 29 are configured to be slightly larger thanthe power generating elements 14 of the unit cells 10. The thickness ofthe sliding plates 28, 29 is not particularly limited, but from theviewpoint of stably realizing the sliding of the unit cells 10, thethickness can be, for example, about 0.5 mm to 5 mm and may be about 1mm to 3 mm.

In step S12, the cell stack S_(B) is compressed in the arrangementdirection Z. Specifically, the cell stack S_(B) is arranged in thecompression area on the rear side Rr of the cell pack assembling device60 so that the height direction H and the arrangement direction Zcoincide. Then, by driving the hydraulic pistons in the compressionarea, the compressing portion 63 is moved to the lower side D tocompress the cell stack S_(B) until the dimension of the cell stackS_(B) in the arrangement direction Z becomes the first dimension A1. Thefirst dimension A1 is a dimension of the left side surface portion 24Land the right side surface portion 24R of the above-describedrestraining hoop portion 24 in the arrangement direction Z, which isequal to the separation distance between the first end plate portion 21and the second end plate portion 22. The first dimension A1 is designedso that the power generating element 14 achieves a desired packingdensity when the dimension of the cell stack S_(B) in the arrangementdirection Z becomes the first dimension A1. The compressed cell stackS_(B) can thus be prepared.

In step S13, the restraint mechanism 20 is prepared. Here, as describedabove, in the restraint mechanism 20, the first end plate portion 21,the second end plate portion 22, and the ring-shaped restraining hoopportion 24 are formed integrally as one constituent element. Thedimension of the left side surface portion 24L and the right sidesurface portion 24R of the restraining hoop portion 24 in thearrangement direction Z is the first dimension A1 matching theseparation distance between the first end plate portion 21 and thesecond end plate portion 22. The expansion suppressing jig 64 is thendisposed with respect to the restraint mechanism 20 so as to restrictthe separation distance between the first end plate portion 21 and thesecond end plate portion 22 from spreading beyond the first dimensionA1. More specifically, the restraint mechanism 20 is disposed in theassembly area on the front side F of the cell pack assembling device 60so that the arrangement direction Z is vertical, and the longitudinaldirection Y is aligned with the front-rear direction. Thereafter, theposition of the expansion suppressing jig 64 in the height direction His adjusted so that the lower surface of the expansion suppressing jig64 comes into contact with the upper surface of the first end plateportion 21.

In step S14, the compressed cell stack S_(B) is inserted between thefirst end plate portion 21 and the second end plate portion 22. Here, bypushing the cell stack S_(B) compressed in the compression area forwardF by the slider mechanism 65, the cell stack S_(B) is moved whilesliding forward F. A frictional force corresponding to “compressionstress×friction coefficient” can be generated when sliding the cellstack S_(B) by the slider mechanism 65. As described above, thecompressive stress of the cell stack S_(B) created by the compressingportion 63 is higher than in the related art. Therefore, the frictionalforce generated when sliding the cell stack S_(B) can become large andcannot be ignored. In the technique disclosed herein, as describedabove, the friction coefficient of the contact surfaces of the slidingplates 28, 29, the lower surface of the compressing portion 63, and theupper surface of the compression area of the base portion 61 issuppressed low, thereby suppressing the friction force.

When sliding the cell stack S_(B), for the purpose of preventing theload on the power generating element 14 and also for the purpose ofrealizing efficient sliding of the cell stack S_(B), it is preferablethat only the side surface on the rear side Rr of the sliding plates 28,29 of the cell stack S_(B) be pushed by the slider mechanism 65. As aresult, the cell stack S_(B) can be inserted between the first end plateportion 21 and the second end plate portion 22 of the restraintmechanism 20. Further, the sliding plates 28, 29 are preferably taperedat the end of the front side F, which is at least the sliding directionin the longitudinal direction Y, so that the thickness decreases towardthe cell stack S_(B) as the front side F is approached. Thisconfiguration is preferable because when the cell stack S_(B) is slidforward F, the cell stack S_(B) is smoothly inserted between the endplate portions 21, 22 without buffering the sliding plates 28, 29 in therestraint mechanism 20. Further, at this time, the expansion suppressingjig 64 is disposed in the restraint mechanism 20. Therefore, it ispossible to suppress the deterioration of the insertability of the cellstack S_(B) due to elastic deformation of the restraining hoop portion24 of the restraint mechanism 20 in the arrangement direction Z duringthe insertion of the cell stack S_(B).

In step S15, the expansion suppressing jig 64 is displaced in adirection in which the separation distance in the arrangement directionZ expands. As a result, the suppressing force of the elastic deformationof the restraint mechanism 20 created by the expansion suppressing jig64 is eliminated. In addition, due to the restraining pressure confinedin the restraint mechanism 20, it is possible to apply a load to theplurality of unit cells 10 in the direction of compressing along thearrangement direction Z, and it is possible to restrain the plurality ofunit cells 10. Thus, the cell pack 1 disclosed herein can be obtained.

As described above, in the present embodiment, the cell stack S_(B) iscompressed and inserted into the restraint mechanism 20 withoutelastically deforming the restraint mechanism 20 in the arrangementdirection. It follows from the above that the cell pack can be producedby replacing a labor-intensive operation of deforming the restraintmechanism 20 having a high tensile strength by compression of the cellstack S_(B) which can be compressed with a lower stress. Further, thereis no need to provide jig holes 21 a, 22 a for inserting the mountingjigs 55 u, 55 d through the end plate portions 21, 22 of the restraintmechanism 20. As a result, it is possible to save the time and eliminatelabor required for machining and realize the restraint mechanism 20having a simple configuration. Furthermore, in the above-describedconfiguration, the separation distance between the pair of end plateportions 21, 22 in the restraint mechanism 20 and the first dimensionA1, which is the dimension of the compressed cell stack S_(B) in thearrangement direction Z, need not to be made completely identical andthere is a certain margin for error. For example, the separationdistance of the end plate portions 21, 22 may be about ±3% to 5%(typically about 0% to −5%) with respect to the first dimension A1 whichis the dimension of the compressed cell stack S_(B) in the arrangementdirection Z. Such an error can be suitably absorbed, for example, byproviding a taper on the front side of the sliding plates 28, 29 in theinsertion direction as described hereinabove.

Disassembling Method 2

The above-described cell pack assembling device 60 can also be suitablyused when disassembling the cell pack 1, for example, by following thedisassembling steps S111 to S114, as shown in FIG. 12. The slidermechanism 65 of the cell pack assembling device 60 may be moved inadvance from the side wall on the rear side Rr of the housing to theside wall on the front side F.

First, in the disassembling step S111, the cell pack 1 is set in thecell pack assembling device 60. Specifically, the cell pack 1 is placedin the assembly area on the front side F. At this time, the cell pack 1is disposed so that the arrangement direction Z of the unit cells 10coincides with the height direction H of the cell pack assembling device60.

Next, in the disassembling step S112, the cell pack 1 is pressurized inthe direction of compressing along the arrangement direction Z.Specifically, the expansion suppressing jig 64 of the cell packassembling device 60 is displaced in a direction of compressing therestraining hoop portion 24 of the cell pack 1 in the arrangementdirection Z. As a result, the separation distance between the end plateportions 21, 22 is reduced in the arrangement direction Z, and thedimension of the cell stack S_(B) in the arrangement direction Z is alsoreduced. At this time, the expansion suppressing jig 64 may be displacedso that the separation distance between the end plate portions 21, 22,that is, the dimension of the compressed cell stack S_(B) in thearrangement direction Z, becomes the second dimension A2.

In the disassembling step S113, the cell stack S_(B) is taken out frombetween the displaced first end plate portion 21 and the second endplate portion 22. Specifically, first, the position of the compressingportion 63 in the height direction H is adjusted so that the distancebetween the lower surface of the compressing portion 63 and the uppersurface of the base portion 61 of the compression area (which can be theupper surface of the spacer) becomes the second dimension A2. Then, thecell stack S_(B) positioned between the end plate portions 21, 22 ispushed toward the rear side Rr by using the slider mechanism 65, therebyslidably moving the cell stack S_(B) rearward Rr. The cell stack S_(B)can thus be taken out from the restraint mechanism 20 of the cell pack 1and moved to the space between the base portion 61 and the compressingportion 63 in the compression area. In the method for disassembling thecell pack disclosed herein, the compression area functions as a pressurerelease area. The sliding plates 28, 29 are disposed on the upper side Uand lower side D of the cell stack S_(B). As a result, the sliding ofthe cell stack S_(B) can be implemented while suppressing the frictionalforce to a low level. Further, the distance between the lower surface ofthe compressing portion 63 and the upper surface of the base portion 61is adjusted to be the second dimension A2. Thus, it is possible to takeout the cell stack S_(B) from the restraint mechanism 20 whilepreventing the slid cell stack S_(B) from scattering to the peripheryfollowing the abrupt release of the restraining force. Further, sincethe end portions of the sliding plates 28, 29 in the longitudinaldirection Y are tapered, the cell stack S_(B) can be slid whilesuppressing the interference of the sliding plates 28, 29 with thecompressing portion 63 and the base portion 61.

In the disassembling step S114, the compression of the restraining hoopportion 24 by the expansion suppressing jig 64 is released and therestraining pressure is released from the cell stack S_(B).Specifically, the expansion suppressing jig 64 is displaced in thedirection in which the distance between the end plate portions 21, 22increases. This makes it possible to release the compressive stressapplied to the restraining hoop portion 24 in the arrangement directionby the expansion suppressing jig 64. Further, the compressing portion 63is displaced in the direction in which the distance from the baseportion 61 increases. This makes it possible to release the restrainingforce applied to the cell stack S_(B) taken out between the compressingportion 63 and the base portion 61. It is preferable that thedisplacement of the compressing portion 63 be performed slowly in orderto suppress the scattering of the unit cells 10 due to the abruptrelease of the restraining force from the cell stack S_(B). As a result,it is possible to release the restraining pressure from the cell stackS_(B) in which the restraining pressure is confined, and to disassemblethe cell pack 1 safely.

In the method for producing and method for disassembling the cell pack1, the first end plate portion 21, the second end plate portion 22, andthe restraining hoop portion 24 are formed integrally. However, such aconfiguration of the cell pack 1 is not limiting. Thus, the productionmethod and the disassembling method described above can be used evenwhen, for example, the first end plate portion 21, the second end plateportion 22, and the restraining hoop portion 24 are formed as separateconstituent elements. Further, in the above-described production methodand disassembling method, the dimension of the first end plate portion21 and the second end plate portion 22 of the cell pack 1 in thelongitudinal direction is made to be the same as the dimension of theleft and right side wall portions 24L, 24R of the restraining hoopportion 24. However, such a configuration of the cell pack 1 is notlimiting. For example, the above-described production method anddisassembling method can be also used when the dimension of the left andright side wall portions 24L, 24R of the restraining hoop portion 24 isless than the dimension of the end plate portions 21, 22 in thelongitudinal direction, or when the restraint mechanism 20 is providedwith two or more restraining hoop portions 24.

Application

In the cell pack 1 disclosed herein, a plurality of unit cells 10 isrestrained by the ring-shaped restraining hoop portion 24 in a statewhere a restraining pressure is applied to the unit cells. With such aconfiguration of the restraining hoop portion 24, the cell pack 1 can berestrained with a high restraining pressure, for example, about 5 timesto about 10 times that in the related art. Such a configuration can beparticularly preferably used for applying a high restraining pressure tothe cell pack 1 having restrained therein a plurality of all-solid statecells in which the internal stress is increased due to a highinterfacial resistance. As a result, it is possible to provide a cellpack 1 composed of all-solid state cells in which, for example, theinternal resistance is reduced with respect to that in the related art.

Further, since the unit cells 10 in such a cell pack 1 can be restrainedwith a high restraining pressure, the present disclosure can beparticularly suitably used in the cell pack 1 for applications in whicha large current is charged and discharged at a high rate. Furthermore,the present disclosure can be particularly suitably used in the cellpack 1 in which the unit cells 10 using the active material having ahigh volume expansion rate during charging and discharging need to berestrained with a high restraining force over a long period of time, inthe cell pack 1 to be used in an environment where vibration or the likeoccurs, and the like. For this reason, examples of suitable applicationsof the cell pack 1 disclosed herein include driving power sourcesmounted on a vehicle such as a plug-in hybrid vehicle (PHV), a hybridvehicle (HV), an electric vehicle (EV) and the like.

Although specific examples of the present disclosure have been describedin detail above, they are merely illustrative and do not limit the scopeof the claims. The techniques set forth in the claims include those inwhich the specific examples described hereinabove are variously modifiedand changed.

For example, the integrally formed restraint mechanism 20 and thesliding plates 28, 29 used in the second embodiment may be individuallyused in the Production Method 1 and the Disassembling Method 1 of thecell pack 1 in the first embodiment. Likewise, the restraint mechanism20, which is used in the first embodiment and in which the end plateportions 21, 22 and the restraining hoop portion 24 are configured asseparate members, may be used in the Production Method 2 and theDisassembling Method 2 of the cell pack 1 in the second embodiment.

What is claimed is:
 1. A method for disassembling a cell pack comprisinga first cell stack in which a plurality of unit cells is arranged in anarrangement direction, and a restraint mechanism for restraining theplurality of unit cells, the restraint mechanism including a first endplate portion disposed at an end portion in a first direction of thearrangement direction of the first cell stack; a second end plateportion disposed at an end portion in a second direction of thearrangement direction of the first cell stack; and a ring-shapedrestraining hoop portion including a first support portion disposed on asurface of the first end plate portion in the first direction, a secondsupport portion disposed on a surface of the second end plate portion inthe second direction, and a pair of side wall portions continuouslyconnecting the first support portion and the second support portionalong the arrangement direction, the method for disassembling including:displacing the first end plate portion relative to the second end plateportion in the first direction so as to extend the restraining hoopportion along the arrangement direction; taking out the first cell stackfrom between the first end plate portion and the second end plateportion; and displacing the displaced first end plate portion relativeto the second end plate portion in the second direction to release theextension of the restraining hoop portion.
 2. A method for disassemblinga cell pack comprising a second cell stack in which a plurality of unitcells is arranged in an arrangement direction, a first sliding plate isdisposed at an end portion in a first direction of the arrangementdirection of the plurality of unit cells, and a second sliding plate isdisposed at an end portion in a second direction of the arrangementdirection of the plurality of unit cells; and a restraint mechanism forrestraining the second cell stack, the restraint mechanism including afirst end plate portion disposed at the end portion in the firstdirection of the arrangement direction of the second cell stack; asecond end plate portion disposed at the end portion in the seconddirection of the arrangement direction of the second cell stack; and aring-shaped restraining hoop portion including a first support portiondisposed on a surface of the first end plate portion in the firstdirection, a second support portion disposed on a surface of the secondend plate portion in the second direction, and a pair of side wallportions continuously connecting the first support portion and thesecond support portion along the arrangement direction, the method fordisassembling including: compressing the cell pack in the arrangementdirection so that the dimension of the second cell stack in thearrangement direction becomes a second dimension; providing a pressurerelease area with a dimension in the arrangement direction equal to thesecond dimension at a position adjacent to the compressed second cellstack in a direction perpendicular to the arrangement direction of thecompressed cell pack; pressing the first sliding plate and the secondsliding plate of the compressed second cell stack in a directionperpendicular to the arrangement direction toward the pressure releasearea, and moving the second cell stack from a space between the firstend plate portion and the second end plate portion to the pressurerelease area; and releasing the compression of the compressed secondcell stack by enlarging the dimension of the pressure release area inthe arrangement direction with respect to the second dimension.